This invention relates to a method for producing a tungsten carbide-nickel grade powder by use of dimolybdenum carbide and tungsten metal powder. The dimolybdenum carbide and tungsten metal powder are used to control the carbon content in the grade powder product. The advantage of using dimolybdenum carbide is that there is more latitude in choosing the lots of tungsten carbide starting material, in grain growth inhibition and a more uniform microstructure in the sintered grade powder product.
Tungsten carbide containing nickel, or more commonly called nickel grade powder is used in the canning industry where a non-magnetic carbide is needed that will not be magnetic when cutting cans. It is used also to make oil seal rings where corrosion must be kept to a minimum. Up to this time this powder has been made using sub-stoichiometric tungsten carbide and nickel metal powder. Stable tungsten carbide has a carbon content of about 6.13% by weight. The sub-stoichiometric tungsten carbide, that is, tungsten carbide having a lower carbon content than the stoichiometric species is necessary to avoid carbon porosity. In order to provide sub-stoichiometric tungsten carbide, either a special low carbon tungsten carbide has to be made or large amounts of tungsten metal powder (WMP) has to be added to a normal (stoichiometric) tungsten carbide to reduce carbon levels. Large quantities of WMP degrade the microstructure of the material and can cause porosity and coarse tungsten carbide clusters and can alter the density of the material.
Therefore a method to produce tungsten carbide-nickel grade powder without the need for sub-stoichiometric tungsten carbide or large amounts of tungsten powder without sacrificing the quality of sintered products made from the powder especially as far as grain growth, microstructure and density, would be very desirable.